Place sugar in a saucepan. Pour water around the sides of the pan. Make an X with your finger across the sugar. Cook over medium-high heat, swirling the pan, until the mixture turns a caramel color. Remove from the heat, add the butter carefully as it will bubble up, add popped corn, and toasted nuts. Pour onto a silicone baking mat or foil lined cookie sheet. Break into clusters while still warm.
To make popcorn on the stove: put 2 to 3 tablespoons oil in a large pot with high sides, and add 1 kernel of corn. Heat oil over medium-high heat until the kernel pops. Add 1/3 cup corn kernels and shake pan continuously until all the kernels are popped.